Lowering of surface melting temperature in atomic clusters with a nearly closed shell structure

We investigate the interplay of particle number, $N$, and structural properties of selected clusters with $N=12$ up to $N=562$ by employing Gupta potentials parameterized for Aluminum and extensive Monte Carlo simulations. Our analysis focuses on closed shell structures with extra atoms. The latter can put the cluster under a significant stress and we argue that typically such a strained system exhibits a reduced energy barrier for (surface) diffusion of cluster atoms. Consequently, also its surface melting temperature, ${T}_{\text{S}}$, is reduced, so that ${T}_{\text{S}}$ separates from and actually falls well below the bulk value. The proposed mechanism may be responsible for the suppression of the surface melting temperature observed in recent experiments.